1. Field of the Invention
The field of the present invention relates to multi-beam laser control systems which are capable of compensating for wavefront distortions in a laser beam traveling from its source to a remote target through an atmospheric path, imaging the target in real time, and selecting and maintaining a suitable hitspot location on the target.
2. Background
Lasers are often operated in applications that require tracking and phase correction to form high quality focused spots at targets located substantial distances from the laser source. Due to boundary layer disturbances and other atmospheric turbulence, a laser beam control system is typically employed to maintain high beam quality at the target. The beam control system provides the ability to both sense the phase distortions and to correct them at the laser source. Because the boundary layer and atmospheric distortions are often dynamic, the beam control system is usually operated in closed loop at sufficient bandwidth to keep up with the dynamics of the atmosphere.
One utility for such a system is a set of military applications where it is desirable to focus the energy of a high energy laser (HEL) to achieve maximum intensity at a specified location of a remote target. This laser energy may be generated as a single beam or as a set of multiple coherent beamlets which are tracked and phased to produce a high quality hit spot on the target.
In the case of a single beam laser source, the atmospheric turbulence effect on the HEL beam may be determined by transmitting a second lower power laser beam (or beacon) to the target and then measuring the wavefront phase of the beacon beam return that scatters from the target back into the HEL transmitting aperture. The inverse of the measured wavefront phase pattern is applied to the outgoing HEL beam which then provides the necessary phase correction. This process is well known in the art. An alternate high energy laser beam control architecture suitable for a laser-target engagement scenario is disclosed in U.S. patent application Ser. No. 12/412,547, filed Mar. 27, 2009, the disclosure of which is incorporated herein by reference in its entirety.
In the case of an HEL beam composed of multiple coherent beamlets, one option is to phase the beamlets together at the source and then transmit them as a single coherent beam to the target. However, this approach may require the use of a large beam director on a turret which is heavy and bulky. In addition, for HEL systems on air vehicles, the turret beam director can be disruptive to the aerodynamic performance of the vehicle. For these reasons, it is desirable to implement a multi-beamlet HEL system with many separate small beamlet apertures to make a much lighter, smaller and less intrusive HEL system. However, there is no known technique in the art to point and phase the beamlets in order to make a high quality focused spot on the target at a stable location.